Sliding closures on the spout of receptacles for molten metal are known in a wide variety of embodiments. A sliding closure, which is used in particular to open and close a converter spout opening, is disclosed for example in EP 0 819 488 B1. It comprises a housing frame in which are disposed a stationary refractory closing plate (a so-called base plate) and a refractory sliding plate held in a sliding unit displaceable in relation to said closing plate. The sliding plate can be pressed sealingly with its upper sliding surface against a lower sliding surface of the base plate. The housing frame is fastened releasably to a base plate fixed to the receptacle, the base plate being braceable with its upper sliding surface with a refractory spout head part inserted into the base plate. During casting operation the refractory parts are subjected to a high degree of wear. It is therefore necessary to change them relatively frequently. For this purpose the housing frame must be respectively released from the base plate.
Since, as shown from experience, when using the sliding closure on the converter spout the base plate in particular wears very quickly, it is known from an earlier Swiss patent application No. 00603/08 to dispose moveably in the housing frame a case with at least two base plates in the housing frame, by means of the displacement a worn base plate being able to be removed from the operating position, and replaced by another base plate without the housing frame having to be removed from the base plate. In this way it is possible to maintain the casting operation for longer until the other refractory parts are also due to be changed.
The closing plates for a sliding closure are known to comprise a respective elongate refractory plate surrounded by a sheet metal jacket and which can also be in several parts.